Be careful of anyone who tells you {without trying} that the combination won't work. A few years ago when I was still a Canon user, I received all kinds of advice that a 2X TC wouldn't AF on my Rebel ..... but the combination did.
I have Tamron lenses and I've been told by professionals to use the extender from the lens manufacturer. I have no problems with the 1.4x but I tried the 2x and was not happy with the results. I sent the first one back and had it replaced, same results so I returned it.
Not sure about the Tamron 100-400, but my canon 100-400 I works well with Tamron 1.4x converter on my 7D2. Of course you get expected degradation in quality but all mechanics work pretty much the same (auto focus, etc).
No extender improves image quality. Since you have a Tamron, I would go with the Tamron (but personally I would not add an extender to any zoom lens. BUT, your focusing speed will decrease and your image quality at 400 mm will suffer.
To begin, canon won’t fit on tamron, this being said my 1,4 is almost permanently affix to my 100-400 I loose a bit of definition at 400 but it’s offset by the range I gain
Canon extenders are designed for a select group of Canon L lenses. They are generally not suitable with lenses that are not explicitly on the compatibility list.
Yes, you get only the center point, possibly the 'expanded' center of 5-points at f/8 with the EOS 7DII. As noted in the comments above, the EF 1.4x cannot be physically connected to the Tamron lens, so it is not an option.
When I had a 7DII I often used it with my EF 100-400 f/4.5-5.6 L II and EF 1.4xIII extender. Image quality was very good but, if I remember correctly, I lost all focus points except the single center point and the 4 assist points that surround it. Auto-focus was also a bit slower. What is the max aperture of the Tamron? If it is the same as the Canon then you will also lose focus points.
Thank you. I read that I would lose focus points with the Canon 100-400. Since the maximum aperature is the same for the Tamron, I expect to have to rely on the center focus point.
I have a Canon 7d ii and a Tamron 100-400 mm lens. Does anyone have any experience using the Canon or the Tamron extenders? I am interested in feedback about image quality and maintaining autofocus. Thank you. Bill
I have both. I kept both and use them on my Canon 7D mark ii, 5D mark iii and my 6D. The G2 has several improvements. It focuses faster and seems sharper especially beyond 500 mm. It has a locking mechanism for all zoom lengths but I don't even use it because the zoom is tighter than the G1 so there is no lens creep. I did have to send the first one back to Tamron twice for them to calibrate it. They finally got it right. The G2 does not seem to need any calibration but mine came with a device to self-calibrate it if needed. I kept both because although the G2 is better, my G is perfectly fine up to about 500 mm.
I have both lenses and find them to be very similar in. Image quality. The big difference is the extra 200mm that the Tamron G2 provides. What do you shoot? I use the Tamron for wildlife and can use all the reach I can carry. I can handhold the G2. You also mention that you have the 2.8 70-200 and extenders. I have read that the 2.8 with the 2x extender gives similar results to the original 100-400. Have you made that comparison? Maybe a 100-400 lenses is redundant for you. But another option for getting the Canon 100-400 ii is to buy a refurbished one from Canon Direct. They come with a one year warrantee. I think they are selling for $1799. I have bought many cameras and lenses that way and have never had a problem.
I have it and previously used it with a 7D and now with a 7D ii. Excellent lens. I have used it with an extender and got very good photos with it but under some conditions got CA.